The PCF8575 is a 16-bit I/O expander from Adafruit that provides additional digital input and output pins for microcontrollers with limited I/O capabilities. It communicates with the host microcontroller via the I2C bus, allowing for the control of up to 16 additional digital devices. Common applications include expanding the number of I/O pins on microcontrollers, such as the Arduino UNO, for use in projects that require multiple sensors, buttons, LEDs, or other digital devices.
Pin Number | Pin Name | Description |
---|---|---|
1 | A0 | Address pin 0, used to set the I2C address |
2 | A1 | Address pin 1, used to set the I2C address |
3 | A2 | Address pin 2, used to set the I2C address |
4 | P0 | I/O port 0 |
5 | P1 | I/O port 1 |
... | ... | ... |
19 | P16 | I/O port 16 |
20 | Vss | Ground (0V) |
21 | SDA | I2C Data Line |
22 | SCL | I2C Clock Line |
23 | INT | Interrupt Output (active low) |
24 | Vcc | Supply Voltage |
Here is an example code snippet for initializing the PCF8575 and toggling all pins:
#include <Wire.h>
// PCF8575 I2C address is 0x20(32) if A0, A1, and A2 are connected to GND
#define PCF8575_ADDRESS 0x20
void setup() {
Wire.begin(); // Initialize I2C communications as Master
}
void loop() {
// Write all pins high
Wire.beginTransmission(PCF8575_ADDRESS);
Wire.write(0xFF); // Low byte
Wire.write(0xFF); // High byte
Wire.endTransmission();
delay(1000);
// Write all pins low
Wire.beginTransmission(PCF8575_ADDRESS);
Wire.write(0x00); // Low byte
Wire.write(0x00); // High byte
Wire.endTransmission();
delay(1000);
}
Q: Can I use the PCF8575 with a 3.3V microcontroller? A: Yes, the PCF8575 is compatible with 3.3V logic levels, but ensure that the I2C bus voltage matches the microcontroller's logic level.
Q: How many PCF8575 expanders can I connect to a single I2C bus? A: You can connect up to 8 PCF8575 devices on a single I2C bus by configuring the A0, A1, and A2 pins for different addresses.
Q: What is the purpose of the interrupt pin? A: The interrupt pin can be used to alert the microcontroller when an input state has changed, allowing for more efficient monitoring of the I/O pins.
This documentation provides a comprehensive guide to using the Adafruit PCF8575 I/O expander. For further assistance, consult the manufacturer's datasheet and technical support resources.